In the prior art a method of monolithic integration has been practiced. Monolithic integration means integration within a single wafer or substrate. The prior art method involves forming a single epitaxial growth which has buried layers, then fabricating one device on the top of the wafer, and a second by selectively recessing to the buried epitaxial layers. For example, this technique has been used to demonstrate the integration of lasers and HBTs. There are several disadvantages of this technique. First, this method requires extremely precise recess etching in order to expose the buried epitaxial layers, and thus achieving high yield on high performance devices is difficult. Second, having a second layer of buried layers underneath the first can introduce undesirable performance limitations on devices fabricated on the top structure.
Another prior art method uses regrowth and has been used in As and P-based devices to fabricate photonic integrated circuits on a chip. For example, epi-layers suited for fabricating laser diodes may be grown, patterned and etched, and a different set of epi may be regrown in order to fabricate waveguides or optical modulators. In the GaAs material system, there are also reports of monolithic integration of laser diodes and MESFETs using the regrowth technique, as well as a report of integrated HEMTs and HBTs on a single wafer.
The prior art is described in the following publications: Choi et al., “Monolithic integration of silicon and gallium arsenisde devices”, U.S. Pat. No. 4,774,205, September 1988; Mand et al., “Monolithic integration of optoelectronic and electronic devices”, U.S. Pat. No. 4,847,665, July 1989; Zavracky et al., “Method of making monolithic integrated III-V type laser devices and silicon devices on silicon”, U.S. Pat. No. 4,940,672, July 1990; Kinoshita et al., “Method for making a field effect transistor integrated with an opto-electronic device”, U.S. Pat. No. 5,021,361, June 1991; Tegude et al, “Method of making monolithic integrated optoelectronic modules”, U.S. Pat. No. 5,075,239, December 1991; Dentai et al., “Method for preparation of monolithically integrated devices”, U.S. Pat. No. 5,432,123, July 1995; Cho et al., “Method for monolithic integration of multiple devices on an optoelectronic substrate”, U.S. Pat. No. 6,503,768 B2, January 2003; Fish et al, “Method of making an opto-electronic laser with integrated modulator”, U.S. Pat. No. 6,574,259 B1, June 2003; Bar-Chaim et al., “Monolithic optoelectronic integration of a GaAlAs laser, a field-effect transistor, and a photodiode”, Appl. Phys. Lett., vol. 44, pp. 941-943, (1984); Egawa et al., “Monolithic Integration of AlGaAs/GaAs MQW Laser Diode and GaAs MESFET Grown on Si Using Selective Regrowth”, IEEE Photonics Technology Letters, vol. 4, no. 6, June 1992; Lin et al., “Monolithic Integration of E/D-mode pHEMT and InGaP HBT Technology on 150-mm GaAs wafers”, CS Mantech Conference, Austin Tex., May 14-17 (2007); and Streit et al., “Monolithic HEMT-HBT integration by selective MBE”, IEEE Trans. Elect. Dev., vol. 42, no. 4, (1995), which are incorporated herein by reference.
Group III-nitride compound semiconductor devices, circuits, and systems are typically fabricated from a single epitaxial structure grown on a sapphire, SiC, Si, or GaN substrate. In the prior art, enhancement mode (E-mode) and depletion mode (D-mode) devices have been integrated on a single epitaxial structure through the use of either a selective gate recess etch or selective fluoride plasma treatment as described by M. Micovic, T. Tsen, M. Hu, P. Hashimoto, P. J. Willadsen, I. Milosavljevic, A. Schmitz, M. Antcliffe, D. Zhender, J. S. Moon, W. S. Wong, and D. Chow, “GaN enhancement/depletion-mode FET logic for mixed signal applications,” Electronics Letters, vol. 41, no. 19, pp. 348-350, September 2005, and Y. Cai, Q. Cheng, W. C. W. Tang, K. J. Chen, and K. M. Lau, “Monolithic integration of enhancement- and depletion-mode AlGaN/GaN HEMTs for GaN digital integrated circuits,” in IEDM Tech. Dig., December 2005, pp. 771-774, which are incorporated herein by reference. However, this prior art method has the disadvantage that all the devices are integrated on a single epitaxial structure, which results in less than optimal performance for different types of integrated devices.
Therefore, what is needed is a monolithic integration method for a Group III nitride material system that provides for monolithic integration of different devices on epitaxial structures optimized for the function of each device. The embodiments of the present disclosure answer these and other needs.